PIC16F870-I/SP 查看數據表（PDF） - Microchip Technology

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PIC16F870-I/SP

28/40-Pin, 8-Bit CMOS FLASH Microcontrollers

Microchip Technology 

PIC16F870/871

10.0 ANALOG-TO-DIGITAL

CONVERTER (A/D) MODULE

The Analog-to-Digital (A/D) Converter module has five

inputs for the PIC16F870 and eight for the PIC16F871.

The analog input charges a sample and hold capacitor.

The output of the sample and hold capacitor is the

input into the converter. The converter then generates

a digital result of this analog level via successive

approximation. The A/D conversion of the analog input

signal results in a corresponding 10-bit digital number.

The A/D module has high and low voltage reference

input that is software selectable to some combination

of VDD, VSS, RA2 or RA3.

The A/D converter has a unique feature of being able to

operate while the device is in SLEEP mode. To operate

in sleep, the A/D clock must be derived from the A/D’s

internal RC oscillator.

The A/D module has four registers. These registers

are:

• A/D Result High Register (ADRESH)

• A/D Result Low Register (ADRESL)

• A/D Control Register0 (ADCON0)

• A/D Control Register1 (ADCON1)

The ADCON0 register, shown in Register 10-1, con-

trols the operation of the A/D module. The ADCON1

register, shown in Register 10-2, configures the func-

tions of the port pins. The port pins can be configured

as analog inputs (RA3 can also be the voltage refer-

ence) or as digital I/O.

Additional information on using the A/D module can be

found in the PICmicro™ Mid-Range MCU Family Ref-

erence Manual (DS33023).

REGISTER 10-1: ADCON0 REGISTER (ADDRESS: 1Fh)

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

R/W-0

U-0

R/W-0

ADCS1 ADCS0 CHS2 CHS1 CHS0 GO/DONE

—

bit7

ADON

bit0

R = Readable bit

W = Writable bit

U = Unimplemented bit,

read as ‘0’

- n = Value at POR reset

bit 7-6:

ADCS1:ADCS0: A/D Conversion Clock Select bits

00 = FOSC/2

01 = FOSC/8

10 = FOSC/32

11 = FRC (clock derived from an RC oscillation)

bit 5-3:

CHS2:CHS0: Analog Channel Select bits

000 = channel 0, (RA0/AN0)

001 = channel 1, (RA1/AN1)

010 = channel 2, (RA2/AN2)

011 = channel 3, (RA3/AN3)

100 = channel 4, (RA5/AN4)

101 = channel 5, (RE0/AN5)(1)

110 = channel 6, (RE1/AN6)(1)

111 = channel 7, (RE2/AN7)(1)

bit 2:

GO/DONE: A/D Conversion Status bit

If ADON = 1

1 = A/D conversion in progress (setting this bit starts the A/D conversion)

0 = A/D conversion not in progress (This bit is automatically cleared by hardware when the A/D conversion is complete)

bit 1: Unimplemented: Read as '0'

bit 0:

ADON: A/D On bit

1 = A/D converter module is operating

0 = A/D converter module is shutoff and consumes no operating current

Note 1: These channels are not available on the PIC16F870.

© 1999 Microchip Technology Inc.

Preliminary

DS30569A-page 79

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